1. Field of the Invention
The invention relates to a motor-driven compressor, and more particularly to a motor-driven compressor to be installed on a vehicle.
2. Description of the Related Art
In a hybrid vehicle that travels by using an engine and an electric motor, the ratio of engine operation mode and electric motor operation mode changes according to the running state of the vehicle. Where the aforementioned hybrid vehicle is configured such that a compressor that actuates the refrigeration cycle constituting an air conditioner receives drive power from the engine, the compressor cannot receive the required drive power from the engine at all times. Therefore, hybrid vehicles use a motor-driven compressor that is driven by electric power obtained, for example, from a battery installed on the vehicle. The motor-driven compressor is attached to the vehicle body or engine.
However, a hybrid vehicle is sometimes operated only by the electric motor in a state in which the engine is stopped, for example, in an idle reduction mode, and where the motor-driven compressor is operated when the engine is thus stopped, unpleasant noise is generated inside and outside the vehicle due to the operation of the motor-driven compressor. This noise includes emitted noise that is generated by the operating motor-driven compressor itself and resonance noise generated by vibrations of the motor-driven compressor amplifying vibrations of the vehicle body or engine via the attachment parts of the motor-driven compressor. Accordingly, arts for reducing noise from the motor-driven compressor have been suggested.
Japanese Utility Model Application Publication No. S64-44810 describes a structure in which screws are inserted in through holes of cylindrical mountings attached to a compressor and the screws are screwed into the threaded holes of the attachment body of an engine, thereby mounting the compressor to the attachment body. Further, vibration-damping rubber is wound about the outer circumferential surfaces of the cylindrical mountings. In a state in which the cylindrical mountings with the vibration-damping rubber wound thereon are disposed on the inner side of semicircular curl portions of a base mounting, the base mounting is fixed to the outer side of the compressor by screwing and mounting to the compressor. In this case, the vibration-damping rubber is interposed between the base mounting and the cylindrical mounting and between the compressor and the cylindrical mounting.
In the compressor described in Japanese Utility Model Application Publication No. S64-44810, the transmission of vibrations of the compressor to the cylindrical mountings is reduced by the vibration-damping rubber, and the transmission of vibrations to the attachment body to which the compressor is attached, that is, to the engine, is thus reduced thereby making it possible to reduce resonance noise. However, the problem associated with the compressor described in the aforementioned publication is that the operating noise of the compression mechanism located inside the compressor cannot be prevented from being emitted as emitted noise from the housing thereof.